The ornamental design for a selfsealingpistonring, as shown and described.
FIG. 1 is a perspective view of the piston ring;
FIG. 2 is a front elevation view of the piston ring, with the back elevation, left elevation and right elevation views identical to the front elevation view;
FIG. 3 is a top plan view of the piston ring;
FIG. 4 is a bottom plan view of the piston ring; and,
FIG. 5 is a sectional view of the piston ring taken along line 5—5 of FIG. 1.